linux-kernel - Re: [PATCH v3 06/16] ARM: configs: Everyone who had PANEL_SIMPLE now gets PANEL_SIMPLE

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Date:   Fri, 3 Sep 2021 09:18:26 +0200
From:   Andrzej Hajda <a.hajda@...sung.com>
To:     Doug Anderson <dianders@...omium.org>,
        Olof Johansson <olof@...om.net>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Linus W <linus.walleij@...aro.org>,
        Daniel Vetter <daniel@...ll.ch>,
        DTML <devicetree@...r.kernel.org>,
        Maxime Ripard <mripard@...nel.org>,
        David Airlie <airlied@...ux.ie>,
        DRI mailing list <dri-devel@...ts.freedesktop.org>,
        Arnd Bergmann <arnd@...db.de>,
        Emil Velikov <emil.velikov@...labora.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Russell King <linux@...linux.org.uk>,
        Linux ARM Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-omap <linux-omap@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "moderated list:ARM/SAMSUNG EXYNOS ARM ARCHITECTURES" 
        <linux-samsung-soc@...r.kernel.org>, linux-sunxi@...ts.linux.dev,
        "open list:TEGRA ARCHITECTURE SUPPORT" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v3 06/16] ARM: configs: Everyone who had PANEL_SIMPLE
 now gets PANEL_SIMPLE_EDP

On 02.09.2021 01:10, Doug Anderson wrote:
> Hi,
> 
> On Wed, Sep 1, 2021 at 2:12 PM Olof Johansson <olof@...om.net> wrote:
>>
>> On Wed, Sep 1, 2021 at 1:20 PM Douglas Anderson <dianders@...omium.org> wrote:
>>>
>>> In the patch ("drm/panel-simple-edp: Split eDP panels out of
>>> panel-simple") we split the PANEL_SIMPLE driver in 2. By default let's
>>> give everyone who had the old driver enabled the new driver too. If
>>> folks want to opt-out of one or the other they always can later.
>>>
>>> Signed-off-by: Douglas Anderson <dianders@...omium.org>
>>
>> Isn't this a case where the new option should just have had the old
>> option as the default value to avoid this kind of churn and possibly
>> broken platforms?
> 
> I'm happy to go either way. I guess I didn't do that originally
> because logically there's not any reason to link the two drivers going
> forward. Said another way, someone enabling the "simple panel" driver
> for non-eDP panels wouldn't expect that the "simple panel" driver for
> DP panels would also get enabled by default. They really have nothing
> to do with one another. Enabling by default for something like this
> also seems like it would lead to bloat. I could have sworn that
> periodically people get yelled at for marking drivers on by default
> when it doesn't make sense.
> 
> ...that being said, I'm happy to change the default as you suggest.
> Just let me know.

I guess this is just misunderstanding. Symbol names:
	CONFIG_DRM_PANEL_SIMPLE=y
	CONFIG_DRM_PANEL_SIMPLE_EDP=y
suggests that CONFIG_DRM_PANEL_SIMPLE_EDP is an 'suboption' of 
CONFIG_DRM_PANEL_SIMPLE, but these symbols are independent - old symbol 
has been split into two independent new symbols.
So Doug's approach seems correct to me. Maybe one could change names of 
symbols to avoid confusion(?).

One more thing, I suspect previous patch can break platforms with EDP 
panels. Even if this patch fixes it, maybe it would be better to squash 
these patches? Or add temporal solution to save bisecatability.

Regards
Andrzej

> 
> -Doug
>